This invention relates to a mold release composition for the molding of hydraulic bonding materials, for example, concrete.
Concrete release agents are applied to the molds, forms or other surfaces that come in contact with freshly mixed concrete. The majority of concrete release agents contain hydrocarbon solvents, and/or oils that are known to cause health and fire hazard related problems. For example, compositions currently used are known to cause dermatological problems when contacting the skin of certain people. These compositions also threaten groundwater supplies due to spillage, runoff and overspray. Because spraying is a common method of applying concrete release agents, prolonged breathing of their aerosolized mists can cause respiratory problems. Many of these compositions also have a disagreeable odor. Additionally, these materials are known to create contamination when scrap concrete parts containing transferred mold release material are put in landfills. Attempts to overcome one or more of these disadvantages have included using vegetable oil-based and water-based mold release compositions, but the result has been a lowering of the releasability and effectiveness of the mold release composition.
There is thus a need for an effective mold release composition that is environmentally friendly and less hazardous to persons working with the composition.
The present invention provides a mold release composition for facilitating demolding of hydraulic bonding materials, such as concrete, from molds or other tool surfaces by application of an effective amount of the mold release composition to the mold surfaces. To this end, a mold release composition is provided comprising at least one low vapor pressure hydrocarbon fluid or a blend of low vapor pressure hydrocarbon fluids. In an exemplary embodiment of the present invention, this hydrocarbon fluid is used in combination with a release modifying material. The hydrocarbon fluids in the compositions of the present invention are low vapor pressure fluids having a vapor pressure less than about 0.1 mm Hg at 20xc2x0 C., making the compositions nonhazardous, nonflammable and environmentally friendly, including at least moderate biodegradability. The low vapor pressure hydrocarbon fluid alone exhibits release characteristics for the bonding materials. However, release ease may be improved or augmented by combining the hydrocarbon with a release modifying material, such as an acid bearing material. In the method for using the composition of the present invention, the composition is applied to the molding tool surface prior to molding the article, then following molding and curing of the article, the article is released from the tool surface.
The present invention provides biodegradable release compositions for facilitating the demolding of hydraulic bonding materials, such as concrete, from molds or other surfaces by application of an effective amount of the release composition to the surface, wherein the release composition includes at least one low vapor pressure hydrocarbon fluid. The low vapor pressure hydrocarbon fluid provides superior release and environmental benefits. The hydrocarbon fluid may be combined with a release modifying material, including but not limited to acid bearing materials, such as fatty acids. The raw materials utilized in the composition of the present invention have multiple FDA and EPA approval ratings, even some with direct food contact applications. The mold release composition has a high flash point rating, for example above about 195xc2x0 F. (90.5xc2x0 C.), and a low vapor pressure, generally below about 0.1 mm Hg at 20xc2x0 C., making the composition safer to use not only from the standpoint of fire hazard, but also from the standpoint of worker safety because workers will not have to breathe volatile and often harmful volatilized hydrocarbon fractions. Scrap parts containing transferred release composition of the present invention may be landfilled under stringent regulations due to the moderate to high biodegradability of the raw materials utilized in the composition. The mold release compositions of the present invention are less hazardous to the skin, eye, nose and throat of individuals coming in contact either on a spot or continuing basis.
The mold release compositions of the present invention may also be applied at lower weights to the molds or other substrates, therefore representing not only a cost savings for the customer, but also less release weight percent on the molded concrete article. By way of example, current mold release compositions normally require about 50-90 grams per square meter of tool surface, whereas compositions of the present invention are effective with less than about 50 grams per square meter or less, for example about 20-50 grams per square meter. In addition, the mold release composition exhibits markedly improved xe2x80x9crelease easexe2x80x9d versus products currently in use in production settings. The molded products release very easily from the tool surface, with little to no-mold buildup. Scrap rates due to part breakage are also significantly reduced.
The main ingredient in mold release compositions of the present invention is a low vapor pressure hydrocarbon fluid, wherein low vapor pressure is understood to refer to a vapor pressure on the order of less than 0.1 mm Hg at 20xc2x0 C. This low vapor pressure hydrocarbon fluid is biodegradable, resulting in improved degradation characteristics of the product in landfill applications, i.e. when scrap molded articles are discarded. Use of the low vapor pressure hydrocarbon fluids lessens hazards normally associated with conventional mold release systems, such as high volatility, which exposes the worker to inhalation hazards. Moreover, the hydrocarbon fluid of the present invention is typically non-flammable, thereby lessening the hazards associated with conventional flammable mold release systems.
In one example of the present invention, the low vapor pressure hydrocarbon fluid comprises an isoparaffinic hydrocarbon fluid or is a blend of isoparaffinic hydrocarbon fluids, such as a predominantly C12-C20 isoparaffinic hydrocarbon fluid, which refers to a fluid having as a majority component an isoparaffinic hydrocarbon with 12-20 carbons. Examples of such materials include hydrotreated middle petroleum distillates available from Exxon Mobil Corp. under the names Isopar(copyright) V and Isopar(copyright) M. Isopar(copyright) V is classified with CAS No. 64742-46-7, which covers the process for manufacturing hydrotreated middle petroleum distillates. Isopar(copyright) V is essentially a branched alkane of relatively low vapor pressure consisting predominantly of C12-C20 isoparaffinic hydrocarbons. It has a minimum flash point of about 244xc2x0 F. (118xc2x0 C.), and typically about 262xc2x0 F. (127.7xc2x0 C.). The xe2x80x9cminimum flash pointxe2x80x9d corresponds to the flash point when all the molecular fractions of the hydrocarbon fluid are at the low end, whereas the xe2x80x9ctypical flash pointxe2x80x9d is the flash point most commonly exhibited by the fluid. Isopar(copyright) M is essentially a lower boiling version (i.e. lower molecular weight) of the Isopar(copyright) V, and it has a minimum flash point of about 177xc2x0 F. (80.5xc2x0 C.), and typically about 199xc2x0 F. (93xc2x0 C.). Both of these hydrocarbon fluids further comprise some cycloparaffins and less than 0.1% aromatics. Lower boiling distillates, such as Exxsol(copyright) D110, Exxsol(copyright) D95, Exxate(copyright) 1000, Exxate(copyright) 1200 and Exxate(copyright) 1300, each from Exxon Mobil Corp., may also be used, alone or in combination, for the low vapor pressure hydrocarbon fluid of the present invention. The Exxsol(copyright) fluids are mixed hydrocarbons, specifically, a mixture of normal, cyclo and isoparaffins, and have minimum flash points of about 221xc2x0 F. (105xc2x0 C.) and 200xc2x0 F. (93xc2x0 C.), respectively, and .typically about 244xc2x0 F. (117.7xc2x0 C.) and 205xc2x0 F. (96.1xc2x0 C.), respectively. The Exxate(copyright) fluids are mono-esters, specifically, a mixture of iso-alkyl acetates, and have typical flash points of 212xc2x0 F. (100xc2x0 C.), 225xc2x0 F. (107xc2x0 C.) and 264xc2x0 F. (129xc2x0 C.), respectively hydrocarbon fluid may also comprise a heavy aromatic fluid, such as Aromatic 200 from Exxon Mobil Corp., which has a typical flash point of 219xc2x0 F. (104xc2x0 C.). Polymeric highly branched hydrocarbons also have good release properties. In an example of the present invention, the low vapor pressure hydrocarbon fluid has a molecular weight of at least about 166 g/mol. Additional examples of low vapor pressure hydrocarbon fluids include: linear alpha-olefins, such as Gulftene(copyright) 16 and Gulftene(copyright) 10 from Chevron Phillips Chemical Co.; branched alpha-olefins, such as Vybar(copyright) 825 from Baker Petrolite Corp.; poly alpha-olefins, such as Durasyn(copyright) 174 and Durasyn(copyright) 166 from Albemarle Corp.; and co-isobutylene-butene polymers, such as Indopol(copyright) H100 and Indopol(copyright) H300 from BP Chemical Co. Esters of acid bearing materials may also be used. For example, the hydrocarbon fluid may comprise a fatty acid methyl ester, such as methyl caprylate-caprate, methyl laurate 96, methyl laurate 70, methyl myristate 95, methyl palmitate 95, methyl stearate 95, methyl oleate, methyl coconate and methyl palm kemalate. These methyl esters may be obtained, for example, from Cognis under their Emery(copyright) brand.
In general, it has been found that higher molecular weight hydrocarbons are most effective in compositions of the present invention, but lower molecular weights may also be used. Additionally, mixtures of high and low molecular weight low vapor pressure hydrocarbons may be used. However, it is desirable to keep the minimum flash point rating above 141xc2x0 F. (60.5xc2x0 C.), for example above about 175OF (79.5xc2x0 C.) and advantageously above about 200xc2x0 F. (93xc2x0 C.) for safety purposes. Below 141xc2x0 F., the materials are flammable. In any event, low vapor pressure hydrocarbon fluids, i.e., with a vapor pressure below about 0.1 mm Hg at 20xc2x0 C., provide one or more benefits over conventional hydrocarbon carriers. These low vapor pressure hydrocarbon fluids may be used alone, in combination with each other, or may be blended with naturally occurring oils that are biodegradable. By way of further example, the hydrocarbon fluid may comprise a blend of isoparaffinic and heavy aromatic hydrocarbon fluids, or a blend of isoparaffinic, normal paraffinic, cycloparaffinic and heavy aromatic hydrocarbon fluids.
The compositions of the present invention containing the low vapor pressure hydrocarbon fluid exhibit release characteristics by virtue of the low vapor pressure hydrocarbon by itself. However, this low vapor pressure hydrocarbon fluid may advantageously be combined with a release modifying material. These release modifying materials include, but are not limited to, acid bearing materials compatible with the low vapor pressure hydrocarbon fluid, i.e., the release modifying materials form a homogenous mixture or are uniformly dispersed with the hydrocarbon fluid. In an example of the present invention, the release modifying material is a fatty acid, such as oleic acid, linoleic acid, stearic acid, lauric acid, or a mixture of fatty acids. Other acid bearing release modifying materials include natural mixtures of acids such as tall oil, rosin, rosin oil, etc. Silicon polymers and waxes are also suitable release modifying materials that are compatible with the low vapor pressure hydrocarbon fluids. By way of example of the release modifying material, use of a fatty acid forms a reaction product (chelate) of the acid moiety on the fatty acid with calcium that is contained in the portland cement portion of the concrete. It should be understood to those skilled in the art that other fatty acids or acid functional materials than those listed herein may also be acceptable for use as the release modifying material in the composition of the present invention.
In an example of the present invention in which the composition includes a combination of a low vapor pressure hydrocarbon fluid and a release modifying material, the composition includes 99-1% isoparaffinic hydrocarbon fluid in combination with 1-99% of a release modifying material. For example, a mold release composition of the present invention may include about 99-90% by weight of the hydrocarbon fluid or fluids and 1-10% by weight of the release modifying material. By way of further example, a composition of the present invention may include about 97.5% by weight Isopar(copyright) V and about 2.5% by weight oleic acid.
The mold release compositions of the present invention may further include optional additives. For example, the compositions may include antioxidants, particularly when being applied to steel molds. The compositions of the present invention may further include a thixotrope to allow for non-sagging/movement of the mold release composition after application to the tool surface. The compositions may further include pigments, such as dyes and solid pigmenting materials. The compositions may further include slip agents, such as waxes, polyalkyl siloxanes, polyaryl siloxanes, and co-polymers of both the reactive and nonreactive type, silicon glycols, etc. The compositions may also include fillers, such as calcium carbonate, barytes, talcs, etc. The compositions may further include fragrances, anti-foams, anti-mists, and corrosion inhibitors.
The compositions of the present invention are primarily useful as release agents for the molding of concrete articles, but the invention is not so limited. The compositions may be used with other hydraulic bonding materials or molding media. Other examples of hydraulic bonding materials include but are not limited to alabaster, plaster, and gypsum. The compositions of the present invention may be applied to a mold or other surfaces via curtain coating, spray application, dipping, brushing, wiping, or any other now known or hereafter developed technique, prior to introduction of the molding media composition. The compositions of the present invention prevent chemical, physical and mechanical bonding of the molding media to the tool surface, i.e. the mold, form or any other containing geometry, before and during the cure cycle of the molding media. The compositions of the present invention provide markedly improved release ease compared to conventional, relatively hazardous release systems currently in use. Release properties exist even when the composition of the present invention is applied at significantly lowered film weights to the tool surface than the film weight necessary with conventional systems. Thus, use of the compositions of the present invention may result in a decrease in volume usage, as well as a decrease in the amount of material transfer to scrap moldings, consequently decreasing the volume of release compositions in landfills. Compositions of the present invention that are transferred to scrap moldings are biodegradable, thus providing a benefit to the environment via both decreased air and water pollution.